EXCEPTION_ACCESS_VIOLATION when trying to bpy.ops.scene.new(type='LINK_COPY')
The problem can be solved by using a persistent application handler that is executed once the project file has been fully loaded. bpy.app.handler.load_post allows you to append functions that shall be executed once the loading is completed. The annotation @persistent is required in order to keep the application handler registered even though a different project is loaded. This is required since normally application handlers are freed once a new project is loaded. 

import bpy
from bpy.app.handlers import persistent


@persistent
def load_post(dummy):
    bpy.ops.scene.new(type="LINK_COPY")
    bpy.app.handlers.load_post.remove(load_post)

bpy.app.handlers.load_post.append(load_post)
bpy.ops.wm.open_mainfile(filepath="/path/to/your/file.blend")